The invention generally relates to interventional or surgical procedures, specifically relating to interventional cardiology and other intra-luminal procedures. The invention more particularly concerns a valve mechanism that allows modulation of pressure within a balloon or expandable member attached to, or otherwise located thereon, of a guidewire or other catheter-like instrument.
The use of a balloon attached to the end of a guidewire is not new, see for example U.S. Pat. No. 6,251,084 (Coelho), and U.S. Pat. No. 4,790,813 (Kensey). In this arrangement, the guidewire is actually a small diameter tube, with the lumen therethrough serving to allow fluid to be injected, and with the fluid being an agent used to expand the balloon.
The balloon may serve various functions (e.g., locating and/or securing the wire or associated device within the artery, securing a wire within a catheter, or blocking the distal flow of fluid and/or debris created during one or more of the procedures).
The balloon/guidewire system may be used in various types of therapeutic and/or diagnostic procedures (e.g., percutaneous transluminal angioplasty, stent placement, the placement of ultrasonic or other diagnostic instruments, and the placement of thrombectomy devices, etc.). During the procedure several catheters or elongate instruments (together “catheters”) may be used sequentially, with the same guidewire. Inserting instruments over, or alongside, a single guidewire saves procedural time, since only one guidewire would need to be placed. This approach may also improve safety, and reduce chance of infection, etc.
Inserting a plurality of catheters, whether singularly or concurrently, requires the catheter(s) to be placed over the proximal end of the guidewire. Where the guidewire is arranged with a balloon at or near the distal end, the catheter(s) would need to be passed over any valve located at the proximal end of the guidewire.
Multiple catheters are commonly used when, for example, a physician performs an angiogram or other diagnostic procedure, and then decides to perform angioplasty or other therapeutic procedure or other interventional procedure. Most interventional procedures will require the placement of a guidewire for the subsequent delivery of the interventional instruments, and more recently some guidewires incorporate distal balloons to protect the distal tissues from debris generated during those same procedures. Since treatment and diagnostic procedures are becoming more commonplace, and the advancements in each of these technologies have led to procedures using even more catheters. These catheters are continually getting smaller, which allows the physician to reach tighter arteries and lumens within the body.
For distal protection to be effective the balloon must remain inflated as catheters are exchanged over the guidewire. This necessitates a small diameter valve, which some refer to as a low-profile valve. Self-sealing valves have previously been disclosed; see for example U.S. Pat. No. 3,477,438 (Allen, et al.), U.S. Pat. No. 3,495,594 (Swanson), U.S. Pat. No. 3,837,381 (Arroyo), and U.S. Pat. No. 4,752,287 (Kurtz, et al.). These valves are commonly made from elastic (Allen, et al., and Kurtz, et al.) or resilient (Swanson) materials, and may require pressure in the system to operate (Arroyo). The properties of these valve materials, together with their operational pressures, require various of these valves to have large sealing areas. This does not facilitate the design of smaller catheters. Additionally, the valves would ideally operate over a wide range of pressures; including positive and negative pressures.
Check valves have also been disclosed, see for example U.S. Pat. No. 4,653,539 (Bell), however these are directional valves, and therefore will not operate in both positive and negative pressure environments. Employing a vacuum in the system during navigation will facilitate the securing of the balloon to the guidewire, that is, the balloon will stay folded or otherwise securely pressed against the side of the wire. This may allow the system to navigate tighter vessels or lumens. However, check valves, such as the one disclosed by Bell, do not meet this bi-directional operation need. Additionally, this type of valve, as well as the previously described self-sealing valves, require a syringe or special instrument to allow evacuation around the valve's sealing surface. These syringes or needles must be in-place during the entire evacuation procedure, or the valve will cease the fluid flow. This opens the systems up to situations where malfunctions or equipment breakage may yield an inserted and expanded balloon, which may not readily be collapsed. A system is needed that will allow evacuation without the application of vacuum or other specialized components.
In addition to these stated concerns, the length of time required to complete the procedure is affected by these valves. This procedure time is of concern because of escalating medical costs, as well as the stress on the patient. These valves must allow rapid infusion and evacuation of balloon-filling fluids.
Yet another low profile catheter valve, designed to fit small diameter catheters to navigate small pathways within the body such as blood vessels and ducts, is disclosed in U.S. Pat. No. 4,911,163 (Fina). A syringe is attached to the proximal end of an elongated tubular conduit (e.g. catheter) and used to inflate a distal balloon. Once the balloon is inflated, the catheter is clamped at the proximal end, the syringe is removed, and a plug is inserted into the lumen of the catheter, and then the clamp is removed. The plug is retracted and reinserted to adjust the balloon inflation volume as needed, using this same multi-step procedure. Needless to say, this type of valve is tedious to handle and the need for a separate clamping system further complicates the procedure and may potentially damage the catheter. Certainly the clamping pressures are very high, in order to totally collapse the circular catheter bore such that fluid will not leak (until the plug is inserted). Reinflating the balloon would also cause integrity problems if the catheter were reclamped at the same location.
Another such low profile catheter valve is disclosed in U.S. Pat. No. 6,325,778 (Zadno-Azizi, et al.). This valve features a needle which is inserted coaxially with the guidewire, wherein the needle is arranged to cover a fluid outlet port. The rate of balloon inflation and collapse is limited by the rate at which gas leaves the fluid outlet port. Since the fluid outlet port is radially outward from the guidewire's longitudinal axis, its size is geometrically constrained; that is, the larger diameter of the port, the less strength the guidewire has. Since the guidewire must withstand significant bending and torsional stress during the procedure, the port must be significantly less than the inside diameter of the guidewire, thereby limiting the rate of evacuation of the balloon-filling fluid.
This slow evacuation phenomenon may have been recognized by Coelho, as the disclosure prescribes a vacuum to collapse the balloon. Indeed, the tortuous path in the orifice of the Coelho device, through which the balloon inflation fluid is evacuated, must be nearly as small as the one disclosed by Zadno-Azizi. Here, the orifice must be considerably smaller than the inside diameter of the guidewire, because the path of fluid escape is through a self-sealing valve; and the valve must have sufficient integrity to cause a seal against itself, after an evacuation needle is withdrawn.
A valve which may utilize the overall inside diameter (or bore) of the guidewire is disclosed in U.S. Pat. No. 5,807,330 (Teitelbaum). The two basic concepts disclosed by Teitelbaum are a valve that is basically an insert with threads, wherein the threads secure the valve in the proximal end of the guidewire; and an insert with a press-fit geometry, that is pressed into the proximal end of the guidewire. Both of these concepts suffer similar shortcomings.
The threaded insert requires extremely fine threads, which are expensive and tedious to manufacture even before considering the limited wall thickness of the guidewire available for threading (perhaps only a few thousandths of an inch). Additionally, it is extremely difficult to align small threaded parts of this sort, which leads to misalignment and cross-threading. This problem would be especially prevalent where the same valve was actuated more than once during the same procedure—a common occurrence.
The press-fit geometry requires parts of very tight tolerance, which are also tedious and expensive to produce. Press-fit components are normally manufactured for mechanical support, but press-fitting to cause a gas impermeable seal is possible; however, the insert would require an extremely uniform surface, which mates exactly with the inside surface at the proximal end of the guidewire. It is this guidewire surface which poses great manufacturing challenges.
Boring or machining the inside surface of the guidewire is very challenging because of the fine wall thickness—perhaps only a few thousandths of an inch. Machining of this component may produce irregular wall thinning, since no tube inside and outside is truly concentric, which could lead to premature failure.
The aforementioned threaded and press-fit concepts disclosed by Teitelbaum both suffer manufacturing challenges as well as economic disadvantages. Finally, they have features that may lead to premature failure, necessitating removal of the device, following by re-insertion of a new balloon/guidewire assembly.
It is the intent of the embodiments of the present invention to overcome these and other shortcomings of the prior art.